1. Field of the Invention
The present invention relates to a flow control valve assembly, and more particularly to a flow control valve assembly for regulating the flow rate of the exhaust gases, which are to be recirculated in an exhaust gas recirculation system from the exhaust system to the intake system of an internal combustion engine so as to clean the engine exhaust gases.
2. Description of the Prior Art
Generally speaking, it is considered necessary in the relevant art that the amount of the exhaust gases to be recirculated from the engine exhaust system to the engine intake system be proportional to the amount of an air-fuel mixture to be sucked into the engine body so as to clean the engine exhaust gases. For this purpose, there has been proposed a flow control valve which is operative to regulate the amount of the exhaust gas recirculation by resorting to the fact that the exhaust gas pressure is proportional to the amount of the mixture intake. This prior art control valve has its effective area controlled by having its diaphragm exposed to the exhaust gas pressure. In this instance, however, the exhaust gas pressure acting upon the diaphragm will often be pulsating during its operation, or the diaphragm itself will often be deteriorated by the heat transferred from the exhaust gases. In another proposal, on the other hand, the flow control valve is controlled partly by detecting the variation in the amount of the sucked mixture in terms of the exhaust gas pressure and partly by applying the intake vacuum to the diaphragm. In this instance, however, reliable control of the flow control valve cannot be expected because the intake vacuum becomes the weaker when the supply of the intake mixture into the engine body is the more.